Plate heat exchanger

ABSTRACT

Plate heat exchanger having mainly rectangular plates mounted in a frame. According to the invention the plates (6, 8) are arranged in at least two groups, the plates having port holes of one size being arranged in one group, while plates having port holes of another size are arranged in another group, the plate group having the largest port holes being arranged closest to the inlet (3) while a plate group having smaller port holes (9) is arranged further away from the inlet (3).

This invention relates to a heat exchanger comprising several platesmounted in a frame and mainly rectangular, which plates are tightenedagainst each other and between which heat transfer areas in the form ofheat exchanging passages are formed for through-flow of heat exchangingmedia, of which at least one is conducted to and from the heat exchangervia inlets and outlets arranged at one of its ends, the plates at theircorner parts being provided with openings for forming of inlet andoutlet channels.

Such plate heat exchangers are manufactured in different sizes havingplates the heat transfer areas of which can range from some few squaredecimeters to several square meters. The plate material is chosen withregard to the field of use but usually comprises stainless oracid-resistant steel. For certain purposes titanium is used, which hasexcellent resistance against salt water but is very expensive.

Plate heat exchangers for large flows require inlet and outlet channelshaving large through-flow areas, i.e. large openings in the corner partsof the plates. That means that large parts of the plates have to bestamped away in order to get these large openings. Particularly in thosecases when titanium is used that means that expensive material isstamped away.

In the inlet ports of the plates the flow is normally branched off forflowing through parallel-connected heat exchanging passages. Due to thisfact the flow is reduced in size with the distance from the inlet. Thisfact means that seen from a theoretical point of view the port holes ofthe plates could be made smaller and smaller when the distance betweenthe plates and the inlet becomes greater and greater.

If the port parts of the plates could be made smaller the useful heattransfer area could be made larger within the same raw sheet-metal size.In practice, however, it is not possible to arrange plates provided withport holes becoming smaller and smaller. Firstly, it would mean that itwould be necessary for a plate heat exchanger supplier to have a verygreat number of plates in stock, which is not economically justifiable.Secondly, it would be necessary to have many expensive press tools.

Thus, there is a need in the market of a plate heat exchanger in whichat least certain plates are provided with port-holes, which are smallerthan those of the plates closest to the inlet. At the same time such aheat exchanger partly has to be economically justifiable, partly has tofunction satisfyingly.

By giving the heat exchanger such a design that is mentioned in theclaims the existing needs can be filled.

According to a preferred embodiment the heat exchanger is provided withtwo groups of plates, the plates in one group having port holes mainlyof one and the same size, while the plates in the second group have portholes of another size, which is mainly one and the same. The placing ofthe groups shall be such that the group of plates provided with thelarge port holes are placed closest to the connections of the frameplate. The groups are preferably separated by means of a separationplate arranged preferably by means of gaskets to tighten against theplates of respective groups.

The invention shall in the following be described more in detail withreference to the accompanying Figures, of which

FIG. 1 shows a side view of a heat exchanger according to the inventionhaving two groups of plates;

FIGS. 2a and 2b show plan view of the corner parts of two plates havinglarge and small openings, respectively;

FIG. 3 shows a plan view of the corner part of a plate having a largeopening put on a separation plate with a plate having a smaller openingindicated beneath;

FIGS. 4a and 4b schematically show plan views of parts of plates havingsmall and large openings, respectively, and corresponding heat transferareas; and

FIG. 5 shows a vertical, longitudinal section of a separation plate withplate groups having large and small openings, respectively, indicated inthe corner parts.

In FIG. 1 is by 1 indicated a frame comprising a frame plate 2 having aninlet 3 and an outlet 4, and a pressure plate 5. In the frame partly agroup of plates 6 having large openings 7 in the corner parts and partlya group of plates 8 having smaller openings 9 in the corner parts aremounted. The groups are separated by a separation plate 10.

The corner parts of the plates 6, 8 are shown in FIG. 2, the openings 7and 9, respectively, being surrounded by ring gaskets 11, 12. The outeredge measure a outside the gaskets 11, 12 decide the position of theopenings 7, 9 in the plates.

In FIG. 3 is shown that the openings 7, 9 in the corner parts of platesin two adjacent groups are not concentric since the position of theopenings are decided by the outer edge measure a according to FIG. 2. Inthe Figure an edge gasket is indicated by 13. This one is connected withthe mentioned gasket 11. The edge of the opening 9 is indicated by 14and the edge of the opening of the separation plate by 15. This opening15 has in the Figure for clarity reasons been made somewhat smaller thanthe opening 14 but is in reality mainly of the same size as is that one.The opening 15 is placed such that smallest possible flow resistancearises in the flow from the channel formed by the openings 7 to thechannel formed by the openings 9, and vice versa, when the medium isflowing out of the heat exchanger. When the openings of a plate aresmall, the heat transfer area can be made large, i.e. a larger part ofthe plate is utilized, which is illustrated in the FIGS. 4a and 4b. Inthis connection the positions of the edge and the ring gaskets on theplate are changed which means that if the port holes are made small theposition of the gasket is moved further upwards on the plate. This meansthat the plate gets a larger heat transfer area compared with thesituation when the plate is provided with large port holes.

It is apparent from FIG. 5 how the gasket against the separation platebetween two adjacent plate groups is arranged. The gasket 11 directlyseals against the plane separation plate, while the gasket 12 engages acircular groove in the separation plate.

The invention is, of course, not limited to a heat exchanger having twogroups of plates but three or more groups can be found. The essentialthing is that the plates in each group are provided with port holesmainly of the same size.

Due to the great costs for manufacturing a new heat exchanger plate itis necessary from an economic point of view to use standard plates fromalready existing manufacturing programs when choosing plates havinglarge and small openings, respectively. Thus, it is only necessary tomanufacture a new separation plate in order to get a heat exchangerhaving optimum flowing and heat transfer characteristics.

In order to get a good economic effect the plates of the different plategroups shall be essentially different from each other regarding portsize and therewith heat exchanger area while the outer dimensions arethe same. Thus, the large port in two groups-heat exchangers ought to beat least 50% but not more than 100% larger than is the small port.Further, the number of plates having small ports ought to amount to atleast the half of but not more than 2/3 of the total number of plates.

The total effect of the invention is then that a heat exchanger isprovided which has the good economy of a heat exchanger having platesprovided with small ports but having a capacity corresponding to theconnection dimension of the large port in the plate group being closestto the inlet.

What is claimed is:
 1. In a heat exchanger including a frame, aplurality of heat exchange plates mounted in the frame and havingsubstantially the same rectangular shape and size, said plates beingdisposed in spaced face-to-face relationship and with pairs of adjacentplates sealed to each other to define a series of passages for separateflows of two heat exchanging media therethrough, the corner regions ofthe plates having openings defining inlet and outlet channels forconducting said media to and from the respective passages, theimprovement comprising an inlet connection and an outlet connection forone of said media located at one end of the heat exchanger, said platesbeing arranged in a first group and a second group, said inletconnection communicating through said inlet channels for said one mediumin said first group of plates with said inlet channels for said onemedium in the second group of plates, said first and second groupshaving their said outlet channels for said one medium in communicationwith said outlet connection, said openings in the plates of the firstgroup being of a first size for defining said inlet and outlet channelsfor said one medium, said openings in the plates of the second groupbeing of a second size for defining said inlet and outlet channels forsaid one medium, said second size being substantially smaller than saidfirst size, said openings in the plates of the second group beinglocated eccentrically relative to the corresponding openings in theplates of the first group, each said eccentrically located opening beingdisplaced toward at least one of the two adjacent plate edges from itslocation if it were concentric relative to the corresponding openings inthe plates of the first group, whereby each plate of the second grouphas a substantially larger heat exchange area than each plate of thefirst group.
 2. The improvement of claim 1, in which said first group islocated nearer said one end of the heat exchanger than said secondgroup.
 3. The improvement of claim 1, comprising also gasket ringsclosely surrounding the openings of said first and second sizes, saidopenings being so located that the spacing between the outer diameter ofeach gasket ring and the adjacent plate edges is the same for the platesof said first and second groups.
 4. In a heat exchanger including aframe, a plurality of heat exchange plates mounted in the frame andhaving substantially the same rectangular shape and size, said platesbeing disposed in spaced face-to-face relationship and with pairs ofadjacent plates sealed to each other to define a series of passages forseparate flows of two heat exchanging media therethrough, the cornerregions of the plates having openings defining inlet and outlet channelsfor conducting said media to and from the respective passages, theimprovement comprising inlet and outlet connections for at least one ofsaid media located at one end of the heat exchanger, said plates beingarranged in a first group and a second group, the plates of each grouphaving their said inlet and outlet channels communicating with saidinlet and outlet channels in the plates of the other group, saidopenings in the plates of the first group being of a first size fordefining said inlet and outlet channels for said one medium, saidopenings in the plates of the second group being of a second size fordefining said inlet and outlet channels for said one medium, said secondsize being substantially smaller than said first size, said openings inthe plates of said second group being located eccentrically relative tothe corresponding openings in the plates of the first group, each saideccentrically located opening being displaced toward at least one of thetwo adjacent plate edges from its location if it were concentricrelative to the corresponding openings in the plates of the first group,whereby each plate of the second group has a substantially larger heatexchange area than each plate of said first group, said second group ofplates having its said inlet and outlet channels for said one mediumcommunicating with said inlet and outlet connections by way ofcorresponding channels in said first group of plates.
 5. The improvementof claim 4, comprising also gasket rings closely surrounding theopenings of said first and second sizes, said openings being so locatedthat the spacing between the outer diameter of each gasket ring and theadjacent plate edges is the same for the plates of said first and secondgroups.
 6. The improvement of claim 4, comprising also a separationplate separating said first and second groups from each other, andgasket rings sealing said groups against the separation plate.
 7. Theimprovement of claim 5, comprising also a separation plate separatingsaid first and second groups from each other, said gasket ringsincluding rings sealing said groups against the separation plate.
 8. Theimprovement of claim 4 or 5, in which the openings of said first sizeare at least 50% but not more than 100% larger than the openings of saidsecond size.
 9. The improvement of claim 4 or 5, in which the number ofplates in said second group is at least 1/2 but not more than 2/3 of thetotal number of plates in the first and second groups.
 10. Theimprovement of claim 9, in which the openings of said first size are atleast 50% but not more than 100% larger than the openings of said secondsize.